(a) Field of the Invention
The present invention relates to a thin film transistor array substrate for a liquid crystal display and, more particularly, to a thin film transistor array substrate having a pixel electrode to display images at unit pixel area.
(b) Description of the Related Art
Generally, a liquid crystal display has a structure where a liquid crystal is sandwiched between two substrates each having electrodes. By applying voltages to the respective electrodes, light transmission through the liquid crystal is controlled.
The liquid crystal display bears a matrix-type pixel structure with a plurality of pixels, and a pixel electrode is formed at each pixel region. The pixel electrode is driven by driving signals applied thereto via wiring lines. The pixel regions are defined by the crossing of gate lines and data lines. The gate lines and the data lines are connected to the pixel electrodes via switching circuits such as thin film transistors (TFTs). The switching circuit controls the picture signals applied to the pixel electrode based on the scanning signals from the gate line. A storage capacitor line is provided at each pixel region to form a storage capacitor together with the pixel electrode. The storage capacitor stores the present pixel signals applied to the pixel electrode until the arrival of subsequent pixel signals.
In the process of fabricating the above-structured thin film transistor array substrate, pixel defects are liable to be generated, causing increased production cost. Among such pixel defects, the white defect is easily visible to naked eyes because the pixel is displayed constantly bright. Therefore, it is preferable that the white defect should be shifted into a black defect where the pixel is displayed to be constantly dark.
The white defect is caused by contact failure between the pixel electrode and the switching element, or malfunction of the switching element. A dark image is initially displayed and, as time passes by, current leaks at the pixel electrode so that the pixel voltage is approximated up to the common voltage of the common electrode facing the pixel electrode. This results in a white defect.
Furthermore, the white defect may be caused by short circuit between the data line and the pixel electrode due to the residual conductive material, or short circuit between the pixel electrode and the common electrode.
Among the techniques of repairing such a white defect into a black defect, there is a technique where the pixel electrode is short-circuited with the gate line that is overlapped with the pixel electrode while receiving gate signals from the gate line. In this case, the gate line transmits the gate signals to the switching circuits of the neighboring pixel line. The gate line is overlapped with the pixel electrodes, thereby functioning as a part of storage capacitor.
However, in a liquid crystal display separately having a storage wiring line being provided to form storage capacitors while being overlapped with the pixel electrodes, because the common voltage is transmitted to the separate storage wiring line, there is still a possibility of white defect even with short-circuiting between the storage wiring line and the pixel electrodes.